The present invention pertains to a rubber bearing with different characteristics in the circumferential direction, which is intended for being mounted in a cylindrical mount.
Rubber bearings of various designs are frequently used especially in the automobile industry. They are used especially in components for the wheel suspension, e.g., for mounting, the suspension arms. The bearings consist, in general, of a tubular inner part, which is surrounded by an elastomer and is connected to same by vulcanization. The bearing is mounted in an outer, likewise cylindrical tube section.
It is often desirable to design the bearings such that they have areas with different characteristics in their circumferential direction. To achieve this, recesses are provided in the elastomer. In the areas of these recesses, the bearing will then have a softer characteristic. However, the stress on the elastomer by radially introduced forces is particularly high as a result in the areas. To achieve a uniform transmission of forces and consequently to avoid the crushing of the rubber and to protect the elastomer from a premature wear by excessive stress, it is therefore necessary to stabilize the elastomer by appropriate measures. It is common practice for this to connect the elastomer to an outer part, which is designed as a cylindrical sleeve and consists of, e.g., aluminum or a plastic. This implies an increased manufacturing cost and is therefore disadvantageous for the manufacturing costs. In contrast, if no such stabilizing outer part is used, there will be relatively narrow limits in terms of the achievable characteristic ratio, i.e., the ratio of soft characteristic to hard characteristic, in the case of bearings of the conventional design. Characteristic differences of at most up to 20% are thus obtained, in general.
The primary object of the present invention is therefore to provide a rubber bearing in which comparatively great characteristic differences can be reached in different directions and whose design is simplified compared with the prior-art bearings with great differences between soft and hard characteristic.
According to the invention, a rubber bearing is provided with different characteristics in the circumferential direction. The bearing is intended for being mounted in a cylindrical mounting eye. The bearing comprises an inner part and an elastomer with an essentially cylindrical outer contour, which surrounds the inner part. The outer contour is connected to the inner part by vulcanization and has recesses in some areas to obtain circumferential sections with a softer characteristic. To accomplish the primary object, the outer contour of the cross-sectional area of the inner part has, contrary to its inner contour, a shape deviating from the circular shape. The height of the rubber of the elastomer of the bearing, which is mounted in the mounting eye without a stabilizing outer ring, varies corresponding to the cross section of the inner part, and the inner part has its greatest radial extension in the area of the recesses, and the elastomer, which has an increased pretension in these areas, has its smallest rubber height in the area of the recesses.
According to an embodiment of the present invention, the inner part has a rectangle-like cross-sectional shape, wherein the short sides of this rectangle-like shape are rounded and are designed as a circular segment, arched outwardly in the radial direction. As a result, the inner part will have a great major axis passing through the longitudinal central axis of the bearing and a minor axis extending at right angles thereto. In another possible embodiment, the inner part has the shape of an ellipse, which is flattened at the ends of its principal axis.
According to embodiments of the bearing according to the present invention that are relevant for practice, the ratio of the major axis to the minor axis is 3:2 or 26:17, as a result of which a characteristic ratio of 2:1 can be obtained. By selecting the ratio of the major axis to the minor axis of the inner part and an outer contour of the elastomer that is coordinated with this, different characteristic ratios can be obtained according to the present invention for the bearing.
Thus, while maintaining the basic principle according to the present invention, another advantageous embodiment of the rubber bearing is obtained by slightly modifying the outer contour of the elastomer, in addition to the changed shape of the inner part, by which the rubber height of the elastomer is increased such that the inner part with the elastomer has an external diameter that is greater before the mounting of the bearing than the internal diameter of the mounting eye. It is additionally possible to influence the characteristic ratio by providing locally limited, radially outwardly directed bulges in the elastomer in the vicinity of the recesses. As a result, the rubber height is additionally increased in the area of these bulges before the mounting of the bearing. The elastomer is pushed together in the area of the recesses due to the mounting in the mounting eye, so that the recesses become smaller and the elastomer has again its smallest rubber height in this area. During the intended use of the bearing, the bulges in the elastomer, which were visible before the mounting, act as a travel-limiting buffer against radially directed loads. In view of the fact that this also has a certain effect on the characteristics, it is thus conceivable that the characteristics of the bearing can be specifically influenced by the design of such buffers and their dimensioning. It is always essential for the present invention that the recesses are preserved independently from the outer contour of the elastomer and from the shape of the inner part in the mounted state and they form a cavity between the elastomer and the mount.
If increased pressure builds up as a result under the load of the bearing in a cavity formed by a recess because of the air present in it, a pressure equalization takes place via a channel between this cavity and the respective opposite recess, which channel is provided according to another advantageous embodiment. Thus, if the bearing is sealed correspondingly, it is also conceivable that a liquid damping agent, which can also escape through the channels corresponding to the particular load, can be additionally introduced into the cavities formed.
The rubber bearing according to the present invention has a markedly simplified design due to the elimination of the outer part. This also leads to a considerable advantage in terms of the cost of the bearing according to the present invention compared with prior-art comparable rubber bearings. Furthermore, the resulting weight reduction can be considered to be advantageous.
A very great variability is achieved concerning the characteristic ratios by designing the inner part correspondingly and by possibly additionally modifying the essentially cylindrical outer contour of the elastomer. It is thus possible to obtain, e.g., a characteristic ratio of 2:1, which was able to be accomplished in prior-art bearings only by the use of an outer part. In addition, the particular characteristic ratio can be favorably finely coordinated in a very simple manner.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.